SHR Group Research Articles

ROLE OF BARORECEPTORS IN HYPOTENSION AND RENAL SYMPHATHOINHIBITION INDUCED BY BLOCKADE OF THE MEDIAN PREOPTIC NUCLEUS

The present study sought to evaluated the autonomic and cardiovascular effects of the MnPO inhibition following the sinoaortic denervation. Male Wistar (WT) rats and spontaneously hypertensive rats (SHR; 250‐300g) were anesthetized (ketamine 100mg.kg‐1, b.wt.; and xylazin 20mg.kg‐1, b.wt.), and submitted to sinoaortic denervation. Femoral artery and vein were catheterized and led subcutaneously to exit between the scapulae. In the following day, animals were anesthetized with urethane (1.2g.kg‐1, b.wt.) and instrumented for recording renal sympathetic nerve activity (RSNA) and for nanoinjections of saline (NaCl; 150 mM) and muscimol (GABAA agonist; 4 mM) into the MnPO. In WT group, the inhibition of the MnPO with muscimol reduced MAP in both sham (n=5) and denervated (17.5±0.8 vs. ‐28.0±6.5 mmHg, respectively; 3min; n=5). This response was maintained throughout the experimental period (‐15.9±2.3 vs. ‐22.5±4.3 mmHg; 30min). The sympathoinhibition induced by inhibition of MnPO were similar between sham (‐23.2±1.8%; 3min) and denervated WT rats (‐22.0±5.2%; 3min). In SHR groups, the blockade of the MnPO also promoted decrease in MAP, however this response was greater in denervated SHR (‐44.7 ± 7.1 mmHg; n=4) compared to the sham (‐21.0 ± 5.6 mmHg; n=5). We also observed similar decrease of RSNA induced by MnPO inhibition in SHR (‐34.9±8.2%; 3min) and denervated SHR (37.5±8.6%; 30min). The results demonstrated that aortic and carotids afferents participate in the modulation of autonomic and cardiovascular responses induced by the blockade of the MnPO.SupportCNPq and FAPEG.

Spontaneously Hypertensive Rats Display Exaggerated Increase in Brain Temperature During Acute Physical Exercise in Temperate and Warm Environments

This study aimed at investigating the changes in brain temperature (Tb) in SHR subjected to acute physical exercise in temperate and warm environments. Adult male Wistar and SHR rats were subjected to implantation of an abdominal temperature (Ta) sensor and a guide cannula in the right frontal cortex, that allowed us to insert a themorresistor and measure Tb. After recovery, the animals were familiarized to run on a treadmill, and then, in alternate days, they were subjected to two constant‐speed protocols until fatigue (temperate and warm environments). The tail skin temperature (Ts), Ta and Tb were recorded. In the temperate environment, the SHR group ​​showed greater increase in Tb compared with Control group from the 13th min until the 35th min, greater increase in Ta from the 19th min until the 52th min, and lower tail skin temperature from the 13th until the 21th min of exercise. In the warm environment, the SHR group ​​showed greater increase in Tb from the 11th until the 24th min, and greater increase in Ta from the 9th min until the 36th min. The SHR group exhibited lower physical performance compared with the Control group in temperate and warm environments. We conclude that during acute exercise in temperate and warm environments, hypertensive rats present greater increases in Tb and Ta. Fapemig, Capes, and Cnpq.

Hypotensive and Angiotensin-Converting Enzyme Inhibitory Activities of Eisenia fetida Extract in Spontaneously Hypertensive Rats.

Objectives. This study aimed to investigate the antihypertensive effects of an Eisenia fetida extract (EFE) and its possible mechanisms in spontaneously hypertensive rats (SHR rats). Methods. Sixteen-week-old SHR rats and Wistar-Kyoto rats (WKY rats) were used in this study. Rats were, respectively, given EFE (EFE group), captopril (captopril group), or phosphate-buffered saline (PBS) (normal control group and SHR group) for 4 weeks. ACE inhibitory activity of EFE in vitro was determined. The systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured using a Rat Tail-Cuff Blood Pressure System. Levels of angiotensin II (Ang II), aldosterone (Ald), and 6-keto-prostaglandin F1 alpha (6-keto-PGF1α) in plasma were determined by radioimmunoassay, and serum nitric oxide (NO) concentration was measured by Griess reagent systems. Results. EFE had marked ACE inhibitory activity in vitro (IC50 = 2.5 mg/mL). After the 4-week drug management, SHR rats in EFE group and in captopril group had lower SBP and DBP, lower levels of Ang II and Ald, and higher levels of 6-keto-PGF1α and NO than the SHR rats in SHR group. Conclusion. These results indicate that EFE has hypotensive effects in SHR rats and its effects might be associated with its ACE inhibitory activity.

The effects of acute administration of losartan, angiotensin II type-1 receptor antagonist, on hemodynamics and oxidative stress parameters in malignant hypertensive rats

Malignant hypertension is a severe form of hypertension which pathogenesis is not fully elucidated. The aim of our study was to investigate the role of Angiotensin II on hemodynamic and oxidative stress parameters in model of malignant hypertension by using losartan. Adult males were divided into three groups: normotensive Wister rats, control SHR and losartan treated SHR. Control and SHR group received a single bolus dosage of saline, while the SHR + LOS group received a losartan. Blood pressure, cardiac output, both total peripheral and carotid vascular resistance and carotid blood flow were measured. CAT, SOD and TBARS were determined in the blood samples. The treatment significantly decreased the blood pressure. There was no significant change in cardiac output or carotid blood flow, but treatment resulted in diminishment of vascular resistances, both total peripheral and carotid. There was a tendency to restore the values of SOD activity towards those of the normotensive group, but there were no change in CAT and TBARS levels. Taken together, our results show that a single application of losartan has a strong hypotensive effect. Angiotensin II seems to have a significant role in the malignant hypertension syndrome and it partially affects oxidative stress parameters.

Hydrogen sulphide and tempol treatments improve the blood pressure and renal excretory responses in spontaneously hypertensive rats

Oxidative stress and suppressed H2S production lead to increased renal vascular resistance, disturbed glomerular hemodynamics, and abnormal renal sodium and water handling, contribute to the pathogenesis and maintenance of essential hypertension in man and the spontaneously hypertensive rat. This study investigated the impact of H2S and tempol alone and in combination on blood pressure and renal hemodynamics and excretory functions in the SHR. Groups of WKY rats or SHR (n = 6) were treated for 4 weeks either as controls or received NaHS (SHR + NaHS), tempol (SHR + Tempol), or NaHS plus tempol (SHR + NaHS + Tempol). Metabolic studies were performed on days 0, 14, and 28, thereafter animals were anaesthetized to measure renal hemodynamics and plasma oxidative and antioxidant markers. SHR control rats had higher mean arterial blood pressure (140.0 ± 2 vs. 100.0 ± 3 mmHg), lower plasma and urinary H2S, creatinine clearance, urine flow rate and urinary sodium excretion, and oxidative stress compared to WKY (all p < 0.05). Treatment either with NaHS or with tempol alone decreased blood pressure and oxidative stress and improved renal hemodynamic and excretory function compared to untreated SHR. Combined NaHS and tempol therapy in SHRs caused larger decreases in blood pressure (∼20–22% vs. ∼11–15% and ∼10–14%), increases in creatinine clearance, urinary sodium excretion and fractional sodium excretion and up-regulated the antioxidant status compared to each agent alone (all p < 0.05). These findings demonstrated that H2S and tempol together resulted in greater reductions in blood pressure and normalization of kidney function compared with either compound alone.

Anti-apoptotic and pro-survival effect of protocatechuic acid on hypertensive hearts

Cardiac apoptosis was found in hearts from hypertensive animals, therefore in this study we aimed to evaluate the anti-apoptotic and pro-survival effects of protocatechuic acid (PCA) on hypertensive hearts. At first we found that, sedentary group (SHR)-PCA group’s decreased TUNEL-positive apoptotic cells than SHR group alone. Protein levels of Fas ligand, Fas death receptor, Fas-associated death domain (FADD), Bid, t-Bid, Bax, cytochrome c, activated caspase-8, activated caspase 9 and activated caspase-3 were decreased in SHR-PCA group compared with SHR group. Moreover, SHR-PCA groups increased pro-survival pathway proteins like IGF1, pIGF1R, pPI3K, p-Akt, Bcl-xL, and Bcl-2 than SHR and sedentary normotensive group (WKY). All these finding suggest us that, Protocatechuic acid prevented hypertension-enhanced cardiac Fas-dependent and mitochondria-dependent apoptotic pathways and enhanced cardiac pro-survival pathway in rat models.

Expression of Notch3 and hypertensive renal fibrosis

To examine the expression of notch3 in the kidneys of patients with primary hypertension and rats with spontaneous hypertension, and to explore the relationship of notch3 and hypertension renal fibrosis. Thirteen patients with primary hypertension served as a primary hypertension group (HP group), and 15 patients with kidney tumor served as a control group (CP group). The spontaneous hypertensive rats served as a primary hypertension group (SHR group, n=6), and WKY rats served as a control group (WKY group, n=6). Masson stainning was used to examine the collagen in the kidneys in the SHR group and the WKY group. Immunohistochemical staining was used to detect the levels of Notch3 in kidneys of the patients and the rats. The expression of snail mRNA in the kidneys in the SHR group and the WKY group was examined by real-time PCR. Masson staining showed much more collagen in the SHR group than that in the WKY group (P<0.05); the expression of Notch3 in the HP group was much higher than that in the CP group ( 6.741±0.231 vs 0.763±0.358, P<0.01). The expression of Notch3 in the SHR group was much higher than that in the WKY group (5.487±0.774 vs 0.421±0.163, P<0.01), and The expression of snail mRNA was much higher in the SHR group than that in the WKY group (0.996±0.120 vs 0.208±0.090, P<0.01 ). Notch3 may be related to the occurrence of hypertension renal fibrosis.

Effects of praeruptorin C on blood pressure and expression of phospholamban in spontaneously hypertensive rats

BackgroundThe traditional Chinese medicine Praeruptorin c (Pra-c) has many physiological and pharmacological effects, including antagonistic effects on blood pressure and calcium levels, maintenance of cellular calcium homeostasis, and improved cardiac systolic and diastolic function. It is potentially a novel and versatile drug for the treatment and prevention of cardiovascular diseases. ObjectiveTo explore the possible impact of Pra-c on blood pressure in SHR and its mechanism of action. Materials and methodsTwenty SHR were randomly divided into a Pra-c group [Pra-c was administered intragastrically, 20mgkg−1d−1, n=10] or an untreated control group (n=10), containing 10 age-matched SD rats. Each group of rats was followed for 8 weeks. Before and during the treatment, tail artery systolic blood pressure was measured using a tail-cuff every 2 weeks. After 8 weeks, the rats were sacrificed and RNA was extracted from homogenates of cardiac tissue. Tissue from the left ventricle was fixed, sectioned and H&E stained to assess possible changes in myocardial cell structure and morphology. Semi-quantitative RT-PCR was used to assess changes in phospholamban gene expression in treated and untreated rats. ResultsSHR treated with Pra-c for 8 weeks had a lower systolic pressure than untreated SHR (p<0.05), two measures of cardiac damage, the heart mass index and left ventricle mass index (HMI and LVMI, respectively) were improved, and the level of PLB mRNA expression was lower in the untreated SHR group (p<0.05). Discussion and conclusionWith continuous hypertension, SHR gradually formed or developed cardiac hypertrophy and fibrosis. Pra-c had a clear effect on blood pressure in SHR, and reversed SHR ventricular remodeling by upregulating the gene expression of sarcoplasmic reticulum PLB.

Moderate intensity exercise does not modulate myostatin and follistatin gene expression in the gastrocnemius muscle of spontaneously hypertensive rats with heart failure

The myostatin/follistatin pathway modulates skeletal muscle trophism. Physical exercise has an important role in the heart failure treatment. In this study we evaluated the effects of moderate aerobic physical training on myostatin and follistatin gene expression and trophism in the gastrocnemius of spontaneously hypertensive rats with heart failure. Sixteen‐month‐old SHRs and normotensive Wistar‐Kyoto (WKY) rats were assigned to sedentary or trained groups. Exercise was performed on treadmill, 30 min/day, 5 days/week, 12 m/min for 4 months. Transthoracic echocardiogram was performed at the end of experiment. Gene expression was evaluated by real time RT‐PCR. Fiber cross‐sectional area was measured in HE‐stained histological sections.Statistical analysistwo‐way ANOVA and Tukey.ResultsEchocardiography showed left cardiac chambers dilation and left ventricular systolic and diastolic dysfunction in both SHR groups compared to the WKY groups. Gene expression of myostatin and follistatin did not differ between groups. Cross‐sectional area was reduced in both SHR groups compared to WKY and was not changed by exercise.ConclusionPhysical exercise does not modulate skeletal muscle trophism and myostatin and follistatin gene expression in spontaneously hypertensive rats with heart failure.

The new role of LOX-1 in hypertension induced neuronal apoptosis

Lectin-like oxidized low-density lipoprotein (oxLDL) receptor-1 (LOX-1) was originally identified as a receptor for oxLDL predominantly expressed in endothelial cells. Recently up-regulation of LOX-1 has been implicated in oxidative stress and cell apoptosis in many cell types. However, LOX-1 expression in neurons or regulation of neuronal apoptosis by LOX-1 has not been reported. To investigate the possible roles of LOX-1 in hypertension induced brain damage, we examined the distribution of LOX-1 in cortex and hippocampus and compared its expression in 32-week-old SHR and WKY rats. Immunofluorescence revealed that LOX-1 positive cells were located principally at the cortex involved in sensory information processing and were mainly expressed in neurons. We also found up-regulated mRNA expression of LOX-1, Bax and caspase-3 and down-regulated mRNA expression of Bcl-2 in SHR group. Compared with WKY group, SHR group showed increased LOX-1 positive cells and TUNEL positive cells. Furthermore, double-labeling method indicated that LOX-1 expression was colocalized with TUNEL positive cells, which means that LOX-1 expression was involved in hypertension related cell apoptosis. These findings indicated that LOX-1 expression was up-regulated in the cortex of SHR and its expression has implication in neuronal apoptosis. Elevated Bax/Bcl-2 ratio may be involved under this event.

Anti-apoptotic and pro-survival effects of exercise training on hypertensive hearts

Activated cardiac apoptosis was found in hearts from hypertensive animals, but little information regarding the effects of exercise training on cardiac apoptosis in hypertension is available. The purpose of this study was to evaluate the anti-apoptotic and pro-survival effects of exercise training on hypertensive hearts. 28 spontaneously hypertensive rats were divided into sedentary group (SHR) or underwent running exercise on treadmill for 1 h/day, 5 sessions/wk, for 12 wk (SHR-EX). Fourteen age-matched Wistar Kyoto rats served as a sedentary normotensive group (WKY). After exercise training or sedentary status, the excised hearts were measured by hemotoxylin and eosin staining, terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling (TUNEL) assay, and Western blotting. Fewer TUNEL-positive apoptotic cells were in SHR-EX groups than those in SHR. Protein levels of Fas ligand, Fas death receptor, tumor necrosis factor (TNF)-α, TNF receptor 1, Fas-associated death domain (FADD), activated caspase-8, and activated caspase-3 (Fas-dependent apoptotic pathways), as well as Bid, t-Bid, Bad, p-Bad, Bak, cytochrome c, activated caspase 9, and activated caspase-3 (mitochondria-dependent apoptotic pathways) were decreased in the SHR-EX group compared with the SHR group. Protein levels of IGF-1, IGF-1R, p-PI3K, p-Akt, p-Bad, and Bcl2 (cardiac pro-survival pathway) become more activated in SHR-EX groups than SHR and WKY. Exercise training prevented hypertension-enhanced cardiac Fas-dependent and mitochondria-dependent apoptotic pathways and enhanced cardiac pro-survival pathway in rat models. Our findings demonstrate new therapeutic effects of exercise training on hypertensive hearts for preventing apoptosis and enhancing survival.

Effect of losartan on intracellular free calcium concentration and improved aortic elasticity in spontaneously hypertensive rat

Objective To investigate the effects of losartan on aortic elasticity and remodeling in spontaneously hypertensive rats (spontaneously hypertensive rats SHR). Methods WKY (Wistar - Kyoto ) rats with normal blood pressure and 16 weeks spontaneously hypertensive rats were randomly divided into WKY control group, SHR control group, high dose losartan group (SHR + HL), low doses losartan group (SHR + LL). Each group has six animals which were given normal diet for 24 weeks. Losartan which was dissolved in 10 ml physiological saline was filling in stomach, other groups were filling with physiological saline. Tail arterial blood pressure, kidney tissues calcium concentration, renal small artery hydroxyproline content was measured and small arteries wall thickness of Glomerularwas detected, and the ratio of thickness and inner diameter (MT/LR) in kidney pathological were observed. Results The calcium concentration of SHR group in kidney tissues was [(18.42±2.34)μmol/g], kidney small artery hydroxyproline content was [(8.26±2.02)mg/g], which were greater than WKY group [(11.83±1.98)μmol/g,(5.16±0.98)mg/g] (t＝3.116,3.258,P＜0.05), but the two treatment groups were less than SHR group (t＝2.946,P＜0.05), the difference was significant. Small arteries wall thickness of Glomerular was [(5.25±1.13)μm], the ratio of thickness and inner diameter (MT/LR) was [(9.57±1.78)%], which were greater than WKY group[(4.03±0.16)μm ,(7.12±1.35)%](t＝2.836,3.425,P＜0.05), but the wall thickness of two treatment groups were [(7.64±1.29)%,(7.85±1.32)%], the two treatment groups were less than SHR group (t＝3.512,3.648,P＜0.05). Conclusions Losartanmay inhibit intracellular calcium overload, reduce fibrosis degree and improve renal arteriole resistance and reverse the renal arteriole reconstruction of SHR rats. Key words: Losartan/PD; Hypertension/ME/PA; Kidney/ME; Calcium/ME; Renal artery/DE

Enhancement of Vasorelaxation in Hypertension Following High-Intensity Exercise

Exercise can ameliorate vascular dysfunction in hypertension, but its underlying mechanism has not been explored thoroughly. We aimed to investigate whether the high-intensity exercise could enhance vasorelaxation mediated by insulin and insulin-like growth factor-1 (IGF-1) in hypertension. Sixteen-week-old spontaneously hypertensive rats were randomly divided into non-exercise sedentary (SHR) and high-intensity exercise (SHR+Ex) groups conducted by treadmill running at a speed of 30 m/ min until exhaustion. Age-matched Wistar-Kyoto rats (WKY) were used as the normotensive control group. Immediately after exercise, the agonist-induced vasorelaxation of aortas was evaluated in organ baths with or without endothelial denudation. Selective inhibitors were used to examine the roles of nitric oxide synthase (NOS) and phosphatidylinositol-3 kinase (PI3K) in the vasorelaxation. By adding superoxide dismutase (SOD), a superoxide scavenger, the role of superoxide production in the vasorelaxation was also clarified. We found that, the high-intensity exercise significantly (P < 0.05) induced higher vasorelaxant responses to insulin and IGF-1 in the SHR+Ex group than that in the SHR group; after endothelial denudation and pre-treatment of the PI3K inhibitor, NOS inhibitor, or SOD, vasorelaxant responses to insulin and IGF-1 became similar among three groups; the protein expression of insulin receptor, IGF-1 receptor, and endothelial NOS (eNOS) was significantly (P < 0.05) increased in the SHR+Ex group compared with the SHR group;] the relaxation to sodium nitroprusside, a NO donor, was not different among three groups. Our findings suggested that the high-intensity exercise ameliorated the insulin- and IGF-1-mediated vasorelaxation through the endothelium-dependent pathway, which was associated with the reduced level of superoxide production.

Effects of spironolactone in spontaneously hypertensive adult rats subjected to high salt intake

OBJECTIVE:To evaluate the effect of spironolactone on ventricular stiffness in spontaneously hypertensive adult rats subjected to high salt intake.INTRODUCTION:High salt intake leads to cardiac hypertrophy, collagen accumulation and diastolic dysfunction. These effects are partially mediated by cardiac activation of the renin-angiotensin-aldosterone system.METHODS:Male spontaneously hypertensive rats (SHRs, 32 weeks) received drinking water (SHR), a 1% NaCl solution (SHR-Salt), or a 1% NaCl solution with a daily subcutaneous injection of spironolactone (80 mg.kg-1) (SHR-Salt-S). Age-matched normotensive Wistar rats were used as a control. Eight weeks later, the animals were anesthetized and catheterized to evaluate left ventricular and arterial blood pressure. After cardiac arrest, a double-lumen catheter was inserted into the left ventricle through the aorta to obtain in situ left ventricular pressure-volume curves.RESULTS:The blood pressures of all the SHR groups were similar to each other but were different from the normotensive controls (Wistar = 109±2; SHR = 118±2; SHR-Salt = 117±2; SHR-Salt-S = 116±2 mmHg; P<0.05). The cardiac hypertrophy observed in the SHR was enhanced by salt overload and abated by spironolactone (Wistar = 2.90±0.06; SHR = 3.44±0.07; SHR-Salt = 3.68±0.07; SHR-Salt-S = 3.46±0.05 mg/g; P<0.05). Myocardial relaxation, as evaluated by left ventricular dP/dt, was impaired by salt overload and improved by spironolactone (Wistar = -3698±92; SHR = -3729±125; SHR-Salt = -3342±80; SHR-Salt-S = -3647±104 mmHg/s; P<0.05). Ventricular stiffness was not altered by salt overload, but spironolactone treatment reduced the ventricular stiffness to levels observed in the normotensive controls (Wistar = 1.40±0.04; SHR = 1.60±0.05; SHR-Salt = 1.67±0.12; SHR-Salt-S = 1.45±0.03 mmHg/ml; P<0.05).CONCLUSION:Spironolactone reduces left ventricular hypertrophy secondary to high salt intake and ventricular stiffness in adult SHRs.

Aerobic exercise acutely improves insulin‐ and insulin‐like growth factor‐1‐mediated vasorelaxation in hypertensive rats

Limited information is available concerning the effects of aerobic exercise on vasorelaxation in hypertension. The aim of this study was to investigate the effects of a single bout of aerobic exercise on insulin- and insulin-like growth factor-1 (IGF-1)-induced vasorelaxation in hypertensive rats. Four-month-old spontaneously hypertensive rats were randomly divided into a sedentary group (SHR) and an exercise group (SHR+Ex) subjected to a single bout of aerobic exercise conducted by treadmill running at 21 m min(1) for 1 h. Age-matched Wistar-Kyoto rats were used as a normotensive control group (WKY). Insulin- and IGF-1-induced vasorelaxant responses in the three groups were evaluated by using isolated aortic rings, with or without endothelial denudation, in organ baths. Possible roles of phosphatidylinositol 3-kinase (PI3K) and nitric oxide synthase (NOS) involved in the NO-dependent vasorelaxation were examined by adding selective inhibitors. The role of superoxide was also clarified by adding superoxide dismutase (SOD). In addition, the endothelium-independent vascular responses to sodium nitroprusside (SNP), a NO donor, were examined. The insulin- and IGF-1-induced vasorelaxation was significantly (P < 0.05) decreased in the SHR group compared with the WKY group. This decreased response in SHR was improved by exercise. These vasorelaxant responses among the three groups became similar after endothelial denudation and pretreatment with the PI3K inhibitor, NOS inhibitor or SOD. Also, no difference among groups was found in the SNP-induced vasorelaxation. We concluded that a single bout of aerobic exercise acutely improves insulin- and IGF-1-mediated vasorelaxation in an endothelium-dependent manner in hypertensive rats.

ERK1/2 Mediated The Vasodilatation of Apelin-13 on Vascular Rings of Spontanously Hypertensive Rat &lt;I&gt;in vitro&lt;/I&gt;*

In order to study the effect of G protein-coupled receptor APJ endogenous ligand apelin-13 to the vasoconstriction and relaxation of spontaneously hypertensive rat's vascular rings in vitro and its NO and ERK1/2 pathway,perfusion method in vitro vascular ring and Power-Lab system was used to detect tension on rat's vascular rings. Experimental groups below:Phenylephrine group,Acetylcholine group,apelin-13 group,apelin-13+ PE group,apelin-13+Ach group,PD98059+PE group,PD98059+Ach group,LNNA+PE group,LNNA+Ach group,apelin-13 (preincubation) +PD98059 +PE group,apelin (preincubation)-13 +PD98059 +Ach group,apelin-13 (preincubation)+LNNA+PE group and apelin-13 (preincubation)+LNNA+Ach group,compared with WKY rats. Rats'vascular smooth muscle cells were cultured and the expression of ERK1/2 protein was detected by Western blot. Apelin-13 for the blood vessel with endothelium has demonstrated concentration-dependent vasodilation and SHR WKY in percentage vasodilation,but for the blood vessel without endothelium,apelin-13 shows the role of vascular contraction and SHR WKY in contraction tension. Apelin-13 pre-incubation can reduce the SHR and WKY rats'the reactivity of vascular contraction tension on phenylephrine and increases the relaxation response to acetylcholine. After NOS inhibitors LNNA blocking the formation of NO,the relaxation response of the vascular rings to apelin-13 is significantly inhibited and apelin more pronounced reduces the diastolic response in the SHR group than in the WKY group. This suggests that the vasodilator effect of apelin-13 partly depends on NO-dependent pathway at least and SHR hypertensive rats with NO pathway obstacles reduces the vasodilation of blood vessels to apelin-13. After pre-incubation of ERK1/2 inhibitor PD98059,the response of vascular rings to apelin-13 shows concentration-dependent contraction,which is the same as the blood vessel without endothelium to apelin-13,SHR WKY in contraction tension. PD98059 reversals the apelin-13's vasodilation effect. Western blot analysis showed that apelin-13 promoted the concentration-dependent and time-dependentexpression of pERK1/2. The potent ERK inhibitor PD98059 decreased the expression of pERK1/2. The diastolic reactivity of apelin in ex-vivo vascular rings of SHR is reduced and the effect is mediated by NO pathway and the ERK1/2 pathway.

Abstract 5083: Klotho Gene Delivery Delays and Attenuates Spontaneous Hypertension

Background - Klotho is a recently-discovered anti-aging gene. Knockout of klotho gene shortens the lifespan while over-expression of klotho gene extends lifespan of mice. The prevalence of hypertension increases with age. Therefore, hypertension and related cardiovascular diseases are aging disorders. The expression of klotho was decreased significantly in SHRs. The purpose of this experiment was to test our hypothesis that klotho gene delivery attenuates spontaneous hypertension. Methods and Results- Recombinant adeno-associated virus (AAV-2) carrying mouse klotho full-length cDNA (AAV.mKL) was constructed for in vivo expression of klotho. Four groups of male SHR (4 weeks) (8 rats/group) and 1 group of age-matched WKY rats (5 rats/group) were used. Blood pressure (BP) and body weight (BW) were measured twice in all animals before gene delivery in SHR. Briefly, the 4 groups of SHR received IV injection of AAV.mKL, AAV.LacZ, AAV.GFP, and PBS, respectively. The WKY group received PBS as a control. Following gene delivery, BP and BW was monitored weekly. BPs of SHR groups treated with AAV.LacZ, AAV.GFP, or PBS were significantly higher than that of the WKY group treated with PBS. AAV.mKL delayed and significantly attenuated the elevation of BP without affecting the body weight gain in SHRs. One single dose of AAV.mKL attenuated spontaneous hypertension for up to 12 weeks (length of the study). The systolic BP was 140±3.6, 174±4, and 126±2.8 mmHg for SHR-mKL, SHR-LacZ, and WKY-PBS groups, respectively. AAV.mKL also significantly increased hypotensive responses to acetylcholine, suggesting that klotho gene delivery improved endothelial function. AAV.mKL significantly decreased NADPH oxidase activity and superoxide production in mesenteric resistance arteries. Klotho gene delivery abolished renal damage in SHRs. Conclusion- AAV delivery of mouse klotho gene delayed and attenuated hypertension in SHR. The antihypertensive effect of klotho may be mediated by inhibition of NADPH oxidases. Klotho deficiency may play a role in the development of spontaneous hypertension. This research has received full or partial funding support from the American Heart Association, Greater Southeast Affiliate (Alabama, Florida, Georgia, Louisiana, Mississippi, Puerto Rico &amp; Tennessee).

Favorable cardiac and aortic remodeling in olmesartan-treated spontaneously hypertensive rats

Cardiovascular remodeling contributes to the progression of cardiovascular disease. Thus, our aim was to evaluate the action of long-term treatment with olmesartan on cardiac and aortic adverse remodeling and its relationship with blood pressure (BP) and tensile forces acting on the aortic wall. Five-month-old male rats were divided in: WKY group (n = 6), SHR group (n = 6), and SHRs treated with hydralazine 30 mg/kg/day (SHR-H, n = 8) or olmesartan 10 mg/kg/day (SHR-O, n = 8). Medications were administered for 16 weeks. The SHR group showed hypertension (189 +/- 4 mmHg), cardiomyocyte hypertrophy (+107%), interstitial fibrosis (5.7% vs 1.9% in WKY), and reduced intramyocardial vascularization (9.1% vs 22.8% in WKY). In aorta, the SHRs showed outward hypertrophic remodeling, increased elastic fibers content (+36%), and increased circumferential wall tension (CWT, 2.79 x 10(4) dyne/cm) and tensile stress (TS, 261.4 x 10(4) dyne/cm(2)). Hydralazine and olmesartan decreased BP (-45% approximately) and likewise CWT and TS (-45% and -35% approximately). Both medications prevented left ventricle remodeling, but olmesartan improved cardiomyocyte hypertrophy better than hydralazine. Hydralazine did not alter media hypertrophy, but it enlarged lumen diameter and increased elastic fibers. It is unlikely that olmesartan prevented all aortic alterations. Taken together, long-term control of BP alone is not sufficient to prevent aortic remodeling due to hypertension, but in myocardium it seems to be enough, except for cardiomyocyte hypertrophy. The differential action of olmesartan suggests that it is essential to block growth stimulation by angiotensin II in cardiomyocytes and vascular smooth muscle cells in order to better prevent cardiovascular adverse remodeling due to arterial hypertension.

Pre-pubertal induction of experimental diabetes protects against early renal macrophage infiltration

The present study was undertaken to identify whether the age at induction of experimental diabetes modifies macrophage infiltration in the kidney. Renal macrophage infiltration was studied 10 days after the induction of experimental diabetes in 4-week-old pre-pubertal and 12-week-old adult male rats of normotensive [Wistar-Kyoto (WKY) rats] and hypertensive (spontaneously hypertensive rats, SHRs) background. Renal macrophage infiltration was evaluated by immunohistochemistry for ED1. Plasma glucose levels were similar in all diabetic groups. Adult SHRs were hypertensive, and induction of diabetes did not alter blood pressure (BP) in any group. Induction of diabetes in pre-pubertal rats did not induce macrophage infiltration in the kidney. However, in adult rats, tubulointerstitial macrophage infiltration was increased in both WKY (22.86 +/- 3.93 vs 7.86 +/- 2.16 per high-power field, P < 0.001) and SHR (26.41 +/- 5.91 vs 11.48 +/- 1.23, P < 0.001) groups after induction of diabetes. Glomerular macrophage infiltration was also increased after induction of diabetes in the adult WKY group (1.83 +/- 0.50 vs 1.16 +/- 0.26 per glomerular cross section, P = 0.029), which was not significant in the adult SHRs (2.52 +/- 0.34 vs 1.95 +/- 0.35). We conclude that the pre-pubertal induction of diabetes apparently protects against early renal macrophage infiltration, while the induction of diabetes in adults induces exaggerated macrophage infiltration in the kidney.

Alteration of Leukocyte–Endothelial Cell Interaction During Aging in Retinal Microcirculation of Hypertensive Rats

Hypertension, one of the more common chronic diseases affecting the elderly, has been reported to influence leukocyte-endothelial cell interaction. The leukocyte-mediated inflammatory process contributes to age-related changes in vessels. This study was designed to evaluate age-related changes in leukocyte-endothelial cell interaction in the hypertensive rat retina. Male spontaneous hypertensive rats (SHR; 1.5, 3, 6, 12, and 20 months of age) and age-matched Wistar-Kyoto rats (WKY) were used. The number of accumulated leukocytes was counted in sections of flat-mounted retinal tissue. The expression of intercellular adhesion molecule-1 (ICAM-1) and CD18 (the common beta-chain of ICAM-1 ligands) was evaluated. Retinal thickness was evaluated histologically. The number of accumulated leukocytes and the expression of ICAM-1 and CD18 increased in the aged retina. The number of leukocytes that accumulated and the expression of CD 18 were significantly higher in the SHR group than in the WKY group (P < 0.01). In addition, retinal thickness decreased with age. Leukocyte-endothelial cell interaction increased in the aged retina and these changes were more severe in SHR retina than in WKY retina. This increased interaction was first observed at 3 months, a relatively young age.